钻进中发生卡钻事故，其现象为卡钻前上提钻具一直有阻力，阻力忽_爱下问搜题

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问题单项选择题

钻进中发生卡钻事故，其现象为卡钻前上提钻具一直有阻力，阻力忽大忽小，机械钻速缓慢下降，卡钻后，初始卡点在钻头附近，泵压下降，其卡钻类型为（）。

A、缩径

B、落物

C、坍塌

D、泥包

答案

参考答案：D

完形填空

完型填空
Robert performs his 24-foot boat past willow(柳树) young trees that stick out of the waters of the Mississippi River. __1__ dances off maples(枫树), their branches heavy with __2__ spring leaves. But a _3__ inspection discloses trouble behind the beautiful sight. Rubbish is __4__ in a logjam(浮木阻塞) and hangs from the tree's branches. For the next three hours Robert and his team pull plastic bags, tanks, bottles and __5__ bowling pins out of the water. Then they __6__ for a picnic table caught in the trees. Welcome to the Mississippi River Beautification Project begun in 1997 with Robert's one man __7__ to pick up rubbish __8__ a 400 mile stretch(伸展) of the 2,340 mile river. That year, often working __9__, the 22-year-old fellow cleaned 150 miles of shoreline. At first the project appeared__10__ and useless. But Robert tried his best to find __11 , and with their backing, he soon had a new boat and five-man __12 -the Boom Crane Crew. Last year alone the crew __13_ from the water 44,055 gallon durms,1,104 tires and enough plastic bags to __14__ a football field. Much of the waste will be __15__. "Robert's operation is the only one actually in __16___on the river," says Mark of the Mississippi River Basin Alliance, a union of environmental groups. "It's the __17_I have ever seen in 20 years, and he is inspiring others to do the __18_ ." "The river has given me a livelihood and brought me so much _19_ ," Robert says, "I want to do something in __20_ ."
( )1. A. Sunlight ( )2. A. ripe ( )3. A. wider ( )4. A. placed ( )5. A. ever ( )6. A. come ( )7. A. work ( )8. A. on ( )9. A. alone ( )10. A. large ( )11. A. supporters ( )12. A. family ( )13. A. came ( )14. A. clean ( )15. A. burned ( )16. A. ending ( )17. A. biggest ( )18. A. deed ( )19. A. time ( )20. A. return	B. Air B. brown B. quicker B. piled B. even B. save B. discovery B. in B. strongly B. happy B. workers B. team B. pulled B. cover B. buried B. progress B. earliest B. favor B. joy B. turn	C. Water C. falling C. closer C. trapped C. nearly C. head C. place C. off C. quietly C. impossible C. engineers C. grade C. pushed C. build C. used C. discussion C. latest C. same C. pride C. pay	D. Moonlight D. fresh D. stricter D. thrown D. merely D. fight D. effort D. along D. fiercely D. possible D. pioneers D. class D. appeared D. spread D. recycled D. common D. luckiest D. good D. waste D. trouble

问答题简答题

什么是回流比？回流比大小与哪些因素有关？